Caption: Andre-Marie Ampere (1775-1836), French physicist and pioneer of electrodynamics. Ampere also worked as a mathematician and chemist. His most famous work was from 1820, when he began to study the new field of electromagnetism (then known by the term electrodynamics). He proposed the right-hand screw rule of magnetic deflection around a wire carrying an electric current. He also proved that the deflection of a compass needle by a nearby electric current is proportional to that electric current, a discovery that led to the International System (SI) unit of electric current being named after him. Artwork from the French book A Travers l'Electricite (Georges Dary, Paris, 1900).